The present invention relates to a method of producing an interwoven seam interconnecting two portions of a woven structure, especially for the purpose of making an endless woven band for use, for instance, in the paper-making industry. The invention is further related to an apparatus for performing the above-mentioned method.
Upto now, the production of such interwoven seams was accomplished exclusively manually in such a manner that the ends to be interconnected were frayed, that is, the transversely extending or web weft threads were removed therefrom, to the depth of about 100 to 200 millimeters and over the entire width of the web, and then the weft threads of the one end portion were woven into the other end portion at the warp threads thereof.
Inasmuch as the distance between the individual threads is, in many instances, very small, many times smaller than 100 micrometers, the manual weaving of the seam threads is a very laborious and time-consuming operation. It is especially difficult for the seam weaver to make sure that the next thread gripped by him or her is indeed the thread which comes next in the order of the threads of the respective array. Thread by thread, he or she must make sure that indeed the correct thread of the respective array has been taken out of this array. Should it, for instance, happen that the thread which should have waited for its turn one more time is mistakenly taken out of the respective array and interwoven with the threads of the other array instead of the next thread of the first-mentioned array, there is obtained a so-called crossing fault which makes the entire woven structure worthless and which must be removed in a laborious repair operation. Experience with this manual seam weaving operation has shown that many manhours are lost in the required reweaving and fault-removal operations.
The entire manual operation in interweaving the threads into a woven seam in an 8-meter wide woven web consisting of 0.18 millimeter threads (35 threads per centimeter) consumes, on the average, about 600 manhours. To this, there is to be added the fact that this seam weaving procedure requires a careful and lengthy education (the time of apprenticeship covering a 2-year period) and can be accomplished only by persons who are very handy and posses a high degree of finger dexterity. The seam weaving operation as such requires a high degree of concentration on the part of the weavers and, in addition thereto, it has a detrimental influence on the eyesight and on the general health of the seam weavers. A particular problem in this connection is the necessarily bad posture during the seam weaving operation. Back pains and intervertebral disk problems, consequently, belong to the working day problems of seam weavers.
Because of the special requirements and the long apprenticeship which, in reality, extends far into the actual seam weaving work in most cases, the circle of skilled seam weavers is quite small and exclusive. This is further aggravated by the fact that many apprentices give up this vocation during their apprenticeship, for health or other reasons, and many already working seam weavers give up after having worked in this field for a certain period of time. Owing to these factors, the renumeration of the seam weavers is higher, actually substantially higher, than the general level of wages of skilled workers employed in the web weaving field.
It will be appreciated from this explanation that the cost of the woven structures, such as endless bands, produced in this manual manner and incorporating the manually woven seams is extraordinarily high. Because of the high cost of such woven bands, the paper-manufacturing industry, for example, cannot be expected to store a wide variety or a great number of such endless bands. An additional reason for this reluctance in the paper-manufacturing industry to acquire a substantial stock of such endless webs or bands is that the band length, texture, mesh size and other parameters of the endless band often change from one run to another. On the other hand, the endless band manufacturing industry is incapable of delivering endless bands with the required parameters on short notice, at least in many instances. Furthermore, the special educational and other personal requirements of the seam weavers, who cannot be readily replaced by other personnel, add to the already long delivery time of the endless bands caused by the laboriousness of the seam weaving operation itself. So, for instance, if a seam weaver is ill or on vacation, the seam weaving operation, of necessity, takes correspondingly longer.
For the paper-manufacturing industry, therefore, there is to be added to the pure cost consideration also the problem of the delivery time. Thus, should it happen that a new endless band of particular parameters is needed on short notice, it may be that an endless band having these parameters is not available for delivery within the available time. Consequently, the operation of the paper-manufacturing facility must then either be changed to the production of a different type of paper, or discontinued altogether until the new endless band becomes available, if such change in operation is not possible or not feasible.
It will be appreciated that, in view of the above-mentioned circumstances, many attempts have been already made to mechanize or automate the seam weaving operation; yet, all such previous attempts have been unsuccessful. Only for the tensioning of the woven web and for the formation of the seam loom sheds have there been presented arrangements by means of which the still necessary manual work has been facilitated. One such arrangement is described in an article by J. Haslmeyer appearing on pages 206 to 208 of the April 1972 issue of Textil-Praxis. However, even these conventional arrangements have the disadvantage that they are incapable of avoid the need for a considerable amount of manual work. Incidentally, the above-mentioned amount of manhours required for producing the seam has already taken into account the use of arrangements of this type.